How much play should there be between the barrel and slide?


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777funk
January 4, 2013, 02:09 PM
Curious how much play there should be between the barrel and the slide on an autoloader? I shot a Ruger P90 today and I found I wasn't as accurate as with other pistols I've fired. I looked carefully and I noticed a couple things. There's a little bit of play between the slide and the barrel. I can probably move the barrel side to side (touching the chamber and moving side to side) about 0.020" or maybe a little more. There's obviously got to be some clearance there or the slide would have trouble with binding or have a hard time landing in the right place, but curous if this play is normal. There isn't play at the muzzle end.

Also I notice with the slide back the barrel feels like it's floating (more play in various directions).

I don't know if this is normal. All I've really ever shot much to date is revolvers.

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Wil Terry
January 4, 2013, 02:25 PM
IT REALLY DOES NOT MATTER how sloppy the fit is as long as the slide and barrel lock-up in the same place each time for the next hammer fall.

777funk
January 4, 2013, 02:42 PM
IT REALLY DOES NOT MATTER how sloppy the fit is as long as the slide and barrel lock-up in the same place each time for the next hammer fall.
Sounds like it was me. Maybe I'm too tense during the recoil bounce. I'll see if I can relax my arms and wrists a little bit more as I shoot. I'm not a big pistol shooter but like to be able to hit the bull when I go out with my bro-in-law and father-in-law. He's a retired LE guy so it's embarrassing when I miss the target! lol.

RancherTexas
January 4, 2013, 03:18 PM
You did not say if the slide was back or if the pistol was in battery. If the slide is back, there is usually a lot of barrel wobble. But as someone already said, if it locks up tight in battery,you are good to go.. Another key is how much play is there between the slide and the frame when in battery. There should be very little movement if you shake it side to side. I once tried a used pistol that had a lot of play between slide and frame and accuracy sucked. However, if everything else is good to great, then some gunsmiths can tighten the slide fit.

BCRider
January 4, 2013, 03:20 PM
On a delayed blowback style semi auto if you can wiggle the barrel around by more than a hair's width when the slide is fully in battery then I would suggest it's time to get the gun checked by a smith.

With the delayed blowback style where the barrel angles down then back up during the slide operation the barrel is supposed to wedge up due to the link or angled slot acting on the slide lock pin to engage the barrel lugs firmly with the matching lugs in the slide. At the same time the barrel should be held at the bushing or nose of the slide with very little clearance. Between the barrel being wedged into engagement at the lugs and the positioning of the muzzle at the nose of the slide there is no room for the barrel to do anything but lock up properly and identically each time.

But when in battery if you can move the barrel around with simple finger pressure that spells trouble. It MAY simply be that the gun is fouled up so badly that the fouling is holding things a few thou out of battery. So a good cleaning is a good start. But if you can still move the barrel around at the ejection port with some finger pressure I'd suggest taking it into a smith.

Drail
January 4, 2013, 03:26 PM
I was taught to fit a 1911 match barrel so that when in battery (lockup) approx. .001" of play was present. Just enough room for a layer of oil. As stated above, the only reason you want the fit that close is so that every single time the barrel goes into lockup it does it exactly the same, every time. There is really no need for the fit to be that close on a general purpose pistol. On a competition Bullseye gun it can win or lose the match. So can the wind, or a bad primer or a shooter who is not in control of his breathing.

rcmodel
January 4, 2013, 03:27 PM
It depends on the make & model of gun.

What BCRider said is perfectly true on a match grade 1911.
Not on a mil-spec GI issue 1911 though.

Or on a Glock, or other combat tupperware, or maybe even a Ruger?
It is perfectly normal to be able to move the barrel all over the place on both ends with thumb pressure when it is locked shut on most all of them. A Glock barrel will move up & down almost 3/32" just by pushing down on the breech block for instance.

That is they way they are designed & made.

rc

BCRider
January 4, 2013, 03:34 PM
I guess I'm a bit spoiled then. None of my CZ's or 1911's do anything but lock up solid. I just assumed that this should be true of any handgun. And I guess I was just reminded again of what happens when we "assume".... :D

777funk
January 4, 2013, 04:09 PM
EDIT: Duplicate Post.

777funk
January 4, 2013, 04:58 PM
You did not say if the slide was back or if the pistol was in battery. If the slide is back, there is usually a lot of barrel wobble. But as someone already said, if it locks up tight in battery,you are good to go.. Another key is how much play is there between the slide and the frame when in battery. There should be very little movement if you shake it side to side. I once tried a used pistol that had a lot of play between slide and frame and accuracy sucked. However, if everything else is good to great, then some gunsmiths can tighten the slide fit.
It was locked up (ready to fire) and I noticed that I could push the ejector end around about 0.020". I could see the area where it lands and there's about that much of a gap (about 10 thousandths on either side if I center it). Also the slide to the frame has a little play in it but I'm guessing less than the ejector has.

EDIT: I should add that I can tip the gun sideways (drivers side down, then passenger side down) and I can see that gravity pulls the play to whatever side is down. In other words, tipped one direction the ejection port end of the barrel moves the .020" I mentioned then tipped the other way the opposite happens. Maybe this is ok but I'd have to think it'd effect accuracy to some degree.

rcmodel
January 4, 2013, 08:42 PM
It's a combat / service grade pistol, not a match grade pistol.

If it was a match grade pistol, any movement would be unacceptable.

Since it isn't, it is.

Regardless of all that, I would bet it will shoot 2.5" - 3.0" groups at 25 yards if the shooter can.

rc

777funk
January 5, 2013, 02:10 PM
0.020 per 5" (say barrel plus extractor) translates to

.02 / (5"/12" to get to per foot of distance on this 5" span on the gun) x number of feet the target is away from the gun = amount of error introduced.

So this would be 2.878" at 20 yards (60 feet) if my math is right. And that's assuming maximum swing of the barrel/slide lockup from one end of play to the other.

BCRider
January 5, 2013, 03:06 PM
I suspect that you've answered your own question by the size of the groupings you got from this gun compared to others.

I now know that some play is OK in some guns. But the key, as rc suggested before, is that the barrel must come to rest in the same way each time within the slide. If it doesn't then there's going to be some opening up of the group. So the question is does the math you did seem to describe the results you got on the target?

BSA1
January 5, 2013, 07:54 PM
Oops!

BSA1
January 5, 2013, 07:56 PM
I'm not a big pistol shooter but like to be able to hit the bull when I go out with my bro-in-law and father-in-law.

I think that comment pretty well sums it up. Work on your basics and watch those groups get smaller.

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